1. Field of the Invention
The present invention relates to a method for forming fog by using at least one air stream connected to a tank where the air stream forms homogeneous droplets of a fluid, which droplets flow further in the air stream towards and through at least one outlet for forming a fog.
2. Description of Related Art
The invention further relates to an apparatus for the generation of fog including a tank containing a liquid, in which tank at least one orifice for generation of droplets is contained, which orifice in operation is connected to means for generating a first air stream.
U.S. Pat. No. 4,836,452 describes an artificial fog generator where compressed air is fed into the pipes that are located directly above the liquid level, and high pressure jets are sprayed perpendicularly towards the liquid surface, and bubbles are created, which bubbles fly out of the liquid. The generated bubbles pass through filtering screens where over size bubbles are returned to the liquid, and bubbles of normal size are directed towards an outlet.
The fog that is generated contains small oil bubbles which oil bubbles are stable for a period, but over time, the bubbles might collapse, and droplets are formed. These droplets might have a size so gravity pulls the droplets downwards. The liquid used is oil, and only liquids with a sufficient high surface tension can be used for forming bubbles.
GB 2306887 describes a diffusion hazer containing a haze solution and a mixing jet that drives the solution onto an impingement surface shattering the particles of the solution. The driven air then carries the particles out through the outlet and, thereby, creating a haze-like atmosphere.
The apparatus in GB 2306887 uses air under high pressure to generate droplets. High pressure often leads to an increase in temperature, and means for cooling the high-pressure air are necessary. Generating the high pressure air and afterwards cooling the high pressure air are both power consuming processes. The use of high-pressure air leads to a formation of droplets of different sizes where only the smaller droplets can be used. To avoid big droplets, filter means are used, and the bigger droplets are returned to the liquid. The formation of droplets just to return most of them also leads to much higher power consumption than necessary. The filter means only reduces the content of bigger droplets, and the fog that is generated collapses rather quickly as the bigger droplets fall due to gravity, and where the bigger droplets during the movement downwards hit smaller droplets and are combined with them so the content of droplets in the fog is reduced rather rapidly.
The apparatus known from prior art can only operate in a correct way by using a defined chemical mixture for forming droplet in a correct way. Change of chemical mixture is only possible if the physical behaviour of the mixture is mostly equal. Especially the surface tension of the liquids must be equal.